NFC: Add STMicroelectronics ST95HF driver

This driver supports STMicroelectronics NFC Transceiver
"ST95HF", in in initiator role to read/write ISO14443 Type 4A,
ISO14443 Type 4B and ISO15693 Type5 tags.

The ST95HF datasheet is available here:
http://www.st.com/web/en/resource/technical/document/datasheet/DM00102056.pdf

Signed-off-by: Shikha Singh <[e-mail]>
Signed-off-by: Samuel Ortiz <[e-mail]>

drivers/nfc/Kconfig

···
 source "drivers/nfc/st-nci/Kconfig"
 source "drivers/nfc/nxp-nci/Kconfig"
 source "drivers/nfc/s3fwrn5/Kconfig"
+source "drivers/nfc/st95hf/Kconfig"
 endmenu

drivers/nfc/Makefile

···
 obj-$(CONFIG_NFC_ST_NCI)	+= st-nci/
 obj-$(CONFIG_NFC_NXP_NCI)	+= nxp-nci/
 obj-$(CONFIG_NFC_S3FWRN5)	+= s3fwrn5/
+obj-$(CONFIG_NFC_ST95HF)	+= st95hf/

drivers/nfc/st95hf/Kconfig

···
+config NFC_ST95HF
+	tristate "ST95HF NFC Transceiver driver"
+	depends on SPI && NFC_DIGITAL
+	help
+	This enables the ST NFC driver for ST95HF NFC transceiver.
+	This makes use of SPI framework to communicate with transceiver
+	and registered with NFC digital core to support Linux NFC framework.
+
+	Say Y here to compile support for ST NFC transceiver ST95HF
+	linux driver into the kernel or say M to compile it as module.

drivers/nfc/st95hf/Makefile

···
+#
+# Makefile for STMicroelectronics NFC transceiver ST95HF
+#
+
+obj-$(CONFIG_NFC_ST95HF)	+= st95hf.o
+st95hf-objs			:= spi.o core.o

drivers/nfc/st95hf/core.c

···
+/*
+ * --------------------------------------------------------------------
+ * Driver for ST NFC Transceiver ST95HF
+ * --------------------------------------------------------------------
+ * Copyright (C) 2015 STMicroelectronics Pvt. Ltd. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/nfc.h>
+#include <linux/of_gpio.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
+#include <linux/wait.h>
+#include <net/nfc/digital.h>
+#include <net/nfc/nfc.h>
+
+#include "spi.h"
+
+/* supported protocols */
+#define ST95HF_SUPPORTED_PROT		(NFC_PROTO_ISO14443_MASK | \
+					NFC_PROTO_ISO14443_B_MASK | \
+					NFC_PROTO_ISO15693_MASK)
+/* driver capabilities */
+#define ST95HF_CAPABILITIES		NFC_DIGITAL_DRV_CAPS_IN_CRC
+
+/* Command Send Interface */
+/* ST95HF_COMMAND_SEND CMD Ids */
+#define ECHO_CMD			0x55
+#define WRITE_REGISTER_CMD		0x9
+#define PROTOCOL_SELECT_CMD		0x2
+#define SEND_RECEIVE_CMD		0x4
+
+/* Select protocol codes */
+#define ISO15693_PROTOCOL_CODE		0x1
+#define ISO14443A_PROTOCOL_CODE		0x2
+#define ISO14443B_PROTOCOL_CODE		0x3
+
+/*
+ * head room len is 3
+ * 1 byte for control byte
+ * 1 byte for cmd
+ * 1 byte for size
+ */
+#define ST95HF_HEADROOM_LEN		3
+
+/*
+ * tailroom is 1 for ISO14443A
+ * and 0 for ISO14443B/ISO15693,
+ * hence the max value 1 should be
+ * taken.
+ */
+#define ST95HF_TAILROOM_LEN		1
+
+/* Command Response interface */
+#define MAX_RESPONSE_BUFFER_SIZE	280
+#define ECHORESPONSE			0x55
+#define ST95HF_ERR_MASK			0xF
+#define ST95HF_TIMEOUT_ERROR		0x87
+#define ST95HF_NFCA_CRC_ERR_MASK	0x20
+#define ST95HF_NFCB_CRC_ERR_MASK	0x01
+
+/* ST95HF transmission flag values */
+#define TRFLAG_NFCA_SHORT_FRAME		0x07
+#define TRFLAG_NFCA_STD_FRAME		0x08
+#define TRFLAG_NFCA_STD_FRAME_CRC	0x28
+
+/* Misc defs */
+#define HIGH				1
+#define LOW				0
+#define ISO14443A_RATS_REQ		0xE0
+#define RATS_TB1_PRESENT_MASK		0x20
+#define RATS_TA1_PRESENT_MASK		0x10
+#define TB1_FWI_MASK			0xF0
+#define WTX_REQ_FROM_TAG		0xF2
+
+#define MAX_CMD_LEN			0x7
+
+#define MAX_CMD_PARAMS			4
+struct cmd {
+	int cmd_len;
+	unsigned char cmd_id;
+	unsigned char no_cmd_params;
+	unsigned char cmd_params[MAX_CMD_PARAMS];
+	enum req_type req;
+};
+
+struct param_list {
+	int param_offset;
+	int new_param_val;
+};
+
+/*
+ * List of top-level cmds to be used internally by the driver.
+ * All these commands are build on top of ST95HF basic commands
+ * such as SEND_RECEIVE_CMD, PROTOCOL_SELECT_CMD, etc.
+ * These top level cmds are used internally while implementing various ops of
+ * digital layer/driver probe or extending the digital framework layer for
+ * features that are not yet implemented there, for example, WTX cmd handling.
+ */
+enum st95hf_cmd_list {
+	CMD_ECHO,
+	CMD_ISO14443A_CONFIG,
+	CMD_ISO14443A_DEMOGAIN,
+	CMD_ISO14443B_DEMOGAIN,
+	CMD_ISO14443A_PROTOCOL_SELECT,
+	CMD_ISO14443B_PROTOCOL_SELECT,
+	CMD_WTX_RESPONSE,
+	CMD_FIELD_OFF,
+	CMD_ISO15693_PROTOCOL_SELECT,
+};
+
+static const struct cmd cmd_array[] = {
+	[CMD_ECHO] = {
+		.cmd_len = 0x2,
+		.cmd_id = ECHO_CMD,
+		.no_cmd_params = 0,
+		.req = SYNC,
+	},
+	[CMD_ISO14443A_CONFIG] = {
+		.cmd_len = 0x7,
+		.cmd_id = WRITE_REGISTER_CMD,
+		.no_cmd_params = 0x4,
+		.cmd_params = {0x3A, 0x00, 0x5A, 0x04},
+		.req = SYNC,
+	},
+	[CMD_ISO14443A_DEMOGAIN] = {
+		.cmd_len = 0x7,
+		.cmd_id = WRITE_REGISTER_CMD,
+		.no_cmd_params = 0x4,
+		.cmd_params = {0x68, 0x01, 0x01, 0xDF},
+		.req = SYNC,
+	},
+	[CMD_ISO14443B_DEMOGAIN] = {
+		.cmd_len = 0x7,
+		.cmd_id = WRITE_REGISTER_CMD,
+		.no_cmd_params = 0x4,
+		.cmd_params = {0x68, 0x01, 0x01, 0x51},
+		.req = SYNC,
+	},
+	[CMD_ISO14443A_PROTOCOL_SELECT] = {
+		.cmd_len = 0x7,
+		.cmd_id = PROTOCOL_SELECT_CMD,
+		.no_cmd_params = 0x4,
+		.cmd_params = {ISO14443A_PROTOCOL_CODE, 0x00, 0x01, 0xA0},
+		.req = SYNC,
+	},
+	[CMD_ISO14443B_PROTOCOL_SELECT] = {
+		.cmd_len = 0x7,
+		.cmd_id = PROTOCOL_SELECT_CMD,
+		.no_cmd_params = 0x4,
+		.cmd_params = {ISO14443B_PROTOCOL_CODE, 0x01, 0x03, 0xFF},
+		.req = SYNC,
+	},
+	[CMD_WTX_RESPONSE] = {
+		.cmd_len = 0x6,
+		.cmd_id = SEND_RECEIVE_CMD,
+		.no_cmd_params = 0x3,
+		.cmd_params = {0xF2, 0x00, TRFLAG_NFCA_STD_FRAME_CRC},
+		.req = ASYNC,
+	},
+	[CMD_FIELD_OFF] = {
+		.cmd_len = 0x5,
+		.cmd_id = PROTOCOL_SELECT_CMD,
+		.no_cmd_params = 0x2,
+		.cmd_params = {0x0, 0x0},
+		.req = SYNC,
+	},
+	[CMD_ISO15693_PROTOCOL_SELECT] = {
+		.cmd_len = 0x5,
+		.cmd_id = PROTOCOL_SELECT_CMD,
+		.no_cmd_params = 0x2,
+		.cmd_params = {ISO15693_PROTOCOL_CODE, 0x0D},
+		.req = SYNC,
+	},
+};
+
+/* st95_digital_cmd_complete_arg stores client context */
+struct st95_digital_cmd_complete_arg {
+	struct sk_buff *skb_resp;
+	nfc_digital_cmd_complete_t complete_cb;
+	void *cb_usrarg;
+	bool rats;
+};
+
+/*
+ * structure containing ST95HF driver specific data.
+ * @spicontext: structure containing information required
+ *	for spi communication between st95hf and host.
+ * @ddev: nfc digital device object.
+ * @nfcdev: nfc device object.
+ * @enable_gpio: gpio used to enable st95hf transceiver.
+ * @complete_cb_arg: structure to store various context information
+ *	that is passed from nfc requesting thread to the threaded ISR.
+ * @st95hf_supply: regulator "consumer" for NFC device.
+ * @sendrcv_trflag: last byte of frame send by sendrecv command
+ *	of st95hf. This byte contains transmission flag info.
+ * @exchange_lock: semaphore used for signaling the st95hf_remove
+ *	function that the last outstanding async nfc request is finished.
+ * @rm_lock: mutex for ensuring safe access of nfc digital object
+ *	from threaded ISR. Usage of this mutex avoids any race between
+ *	deletion of the object from st95hf_remove() and its access from
+ *	the threaded ISR.
+ * @nfcdev_free: flag to have the state of nfc device object.
+ *	[alive | died]
+ * @current_protocol: current nfc protocol.
+ * @current_rf_tech: current rf technology.
+ * @fwi: frame waiting index, received in reply of RATS according to
+ *	digital protocol.
+ */
+struct st95hf_context {
+	struct st95hf_spi_context spicontext;
+	struct nfc_digital_dev *ddev;
+	struct nfc_dev *nfcdev;
+	unsigned int enable_gpio;
+	struct st95_digital_cmd_complete_arg complete_cb_arg;
+	struct regulator *st95hf_supply;
+	unsigned char sendrcv_trflag;
+	struct semaphore exchange_lock;
+	struct mutex rm_lock;
+	bool nfcdev_free;
+	u8 current_protocol;
+	u8 current_rf_tech;
+	int fwi;
+};
+
+/*
+ * st95hf_send_recv_cmd() is for sending commands to ST95HF
+ * that are described in the cmd_array[]. It can optionally
+ * receive the response if the cmd request is of type
+ * SYNC. For that to happen caller must pass true to recv_res.
+ * For ASYNC request, recv_res is ignored and the
+ * function will never try to receive the response on behalf
+ * of the caller.
+ */
+static int st95hf_send_recv_cmd(struct st95hf_context *st95context,
+				enum st95hf_cmd_list cmd,
+				int no_modif,
+				struct param_list *list_array,
+				bool recv_res)
+{
+	unsigned char spi_cmd_buffer[MAX_CMD_LEN];
+	int i, ret;
+	struct device *dev = &st95context->spicontext.spidev->dev;
+
+	if (cmd_array[cmd].cmd_len > MAX_CMD_LEN)
+		return -EINVAL;
+	if (cmd_array[cmd].no_cmd_params < no_modif)
+		return -EINVAL;
+	if (no_modif && !list_array)
+		return -EINVAL;
+
+	spi_cmd_buffer[0] = ST95HF_COMMAND_SEND;
+	spi_cmd_buffer[1] = cmd_array[cmd].cmd_id;
+	spi_cmd_buffer[2] = cmd_array[cmd].no_cmd_params;
+
+	memcpy(&spi_cmd_buffer[3], cmd_array[cmd].cmd_params,
+	       spi_cmd_buffer[2]);
+
+	for (i = 0; i < no_modif; i++) {
+		if (list_array[i].param_offset >= cmd_array[cmd].no_cmd_params)
+			return -EINVAL;
+		spi_cmd_buffer[3 + list_array[i].param_offset] =
+						list_array[i].new_param_val;
+	}
+
+	ret = st95hf_spi_send(&st95context->spicontext,
+			      spi_cmd_buffer,
+			      cmd_array[cmd].cmd_len,
+			      cmd_array[cmd].req);
+	if (ret) {
+		dev_err(dev, "st95hf_spi_send failed with error %d\n", ret);
+		return ret;
+	}
+
+	if (cmd_array[cmd].req == SYNC && recv_res) {
+		unsigned char st95hf_response_arr[2];
+
+		ret = st95hf_spi_recv_response(&st95context->spicontext,
+					       st95hf_response_arr);
+		if (ret < 0) {
+			dev_err(dev, "spi error from st95hf_spi_recv_response(), err = 0x%x\n",
+				ret);
+			return ret;
+		}
+
+		if (st95hf_response_arr[0]) {
+			dev_err(dev, "st95hf error from st95hf_spi_recv_response(), err = 0x%x\n",
+				st95hf_response_arr[0]);
+			return -EIO;
+		}
+	}
+
+	return 0;
+}
+
+static int st95hf_echo_command(struct st95hf_context *st95context)
+{
+	int result = 0;
+	unsigned char echo_response;
+
+	result = st95hf_send_recv_cmd(st95context, CMD_ECHO, 0, NULL, false);
+	if (result)
+		return result;
+
+	/* If control reached here, response can be taken */
+	result = st95hf_spi_recv_echo_res(&st95context->spicontext,
+					  &echo_response);
+	if (result) {
+		dev_err(&st95context->spicontext.spidev->dev,
+			"err: echo response receieve error = 0x%x\n", result);
+		return result;
+	}
+
+	if (echo_response == ECHORESPONSE)
+		return 0;
+
+	dev_err(&st95context->spicontext.spidev->dev, "err: echo res is 0x%x\n",
+		echo_response);
+
+	return -EIO;
+}
+
+static int secondary_configuration_type4a(struct st95hf_context *stcontext)
+{
+	int result = 0;
+	struct device *dev = &stcontext->nfcdev->dev;
+
+	/* 14443A config setting after select protocol */
+	result = st95hf_send_recv_cmd(stcontext,
+				      CMD_ISO14443A_CONFIG,
+				      0,
+				      NULL,
+				      true);
+	if (result) {
+		dev_err(dev, "type a config cmd, err = 0x%x\n", result);
+		return result;
+	}
+
+	/* 14443A demo gain setting */
+	result = st95hf_send_recv_cmd(stcontext,
+				      CMD_ISO14443A_DEMOGAIN,
+				      0,
+				      NULL,
+				      true);
+	if (result)
+		dev_err(dev, "type a demogain cmd, err = 0x%x\n", result);
+
+	return result;
+}
+
+static int secondary_configuration_type4b(struct st95hf_context *stcontext)
+{
+	int result = 0;
+	struct device *dev = &stcontext->nfcdev->dev;
+
+	result = st95hf_send_recv_cmd(stcontext,
+				      CMD_ISO14443B_DEMOGAIN,
+				      0,
+				      NULL,
+				      true);
+	if (result)
+		dev_err(dev, "type b demogain cmd, err = 0x%x\n", result);
+
+	return result;
+}
+
+static int st95hf_select_protocol(struct st95hf_context *stcontext, int type)
+{
+	int result = 0;
+	struct device *dev;
+
+	dev = &stcontext->nfcdev->dev;
+
+	switch (type) {
+	case NFC_DIGITAL_RF_TECH_106A:
+		stcontext->current_rf_tech = NFC_DIGITAL_RF_TECH_106A;
+		result = st95hf_send_recv_cmd(stcontext,
+					      CMD_ISO14443A_PROTOCOL_SELECT,
+					      0,
+					      NULL,
+					      true);
+		if (result) {
+			dev_err(dev, "protocol sel, err = 0x%x\n",
+				result);
+			return result;
+		}
+
+		/* secondary config. for 14443Type 4A after protocol select */
+		result = secondary_configuration_type4a(stcontext);
+		if (result) {
+			dev_err(dev, "type a secondary config, err = 0x%x\n",
+				result);
+			return result;
+		}
+		break;
+	case NFC_DIGITAL_RF_TECH_106B:
+		stcontext->current_rf_tech = NFC_DIGITAL_RF_TECH_106B;
+		result = st95hf_send_recv_cmd(stcontext,
+					      CMD_ISO14443B_PROTOCOL_SELECT,
+					      0,
+					      NULL,
+					      true);
+		if (result) {
+			dev_err(dev, "protocol sel send, err = 0x%x\n",
+				result);
+			return result;
+		}
+
+		/*
+		 * delay of 5-6 ms is required after select protocol
+		 * command in case of ISO14443 Type B
+		 */
+		usleep_range(50000, 60000);
+
+		/* secondary config. for 14443Type 4B after protocol select */
+		result = secondary_configuration_type4b(stcontext);
+		if (result) {
+			dev_err(dev, "type b secondary config, err = 0x%x\n",
+				result);
+			return result;
+		}
+		break;
+	case NFC_DIGITAL_RF_TECH_ISO15693:
+		stcontext->current_rf_tech = NFC_DIGITAL_RF_TECH_ISO15693;
+		result = st95hf_send_recv_cmd(stcontext,
+					      CMD_ISO15693_PROTOCOL_SELECT,
+					      0,
+					      NULL,
+					      true);
+		if (result) {
+			dev_err(dev, "protocol sel send, err = 0x%x\n",
+				result);
+			return result;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void st95hf_send_st95enable_negativepulse(struct st95hf_context *st95con)
+{
+	/* First make irq_in pin high */
+	gpio_set_value(st95con->enable_gpio, HIGH);
+
+	/* wait for 1 milisecond */
+	usleep_range(1000, 2000);
+
+	/* Make irq_in pin low */
+	gpio_set_value(st95con->enable_gpio, LOW);
+
+	/* wait for minimum interrupt pulse to make st95 active */
+	usleep_range(1000, 2000);
+
+	/* At end make it high */
+	gpio_set_value(st95con->enable_gpio, HIGH);
+}
+
+/*
+ * Send a reset sequence over SPI bus (Reset command + wait 3ms +
+ * negative pulse on st95hf enable gpio
+ */
+static int st95hf_send_spi_reset_sequence(struct st95hf_context *st95context)
+{
+	int result = 0;
+	unsigned char reset_cmd = ST95HF_COMMAND_RESET;
+
+	result = st95hf_spi_send(&st95context->spicontext,
+				 &reset_cmd,
+				 ST95HF_RESET_CMD_LEN,
+				 ASYNC);
+	if (result) {
+		dev_err(&st95context->spicontext.spidev->dev,
+			"spi reset sequence cmd error = %d", result);
+		return result;
+	}
+
+	/* wait for 3 milisecond to complete the controller reset process */
+	usleep_range(3000, 4000);
+
+	/* send negative pulse to make st95hf active */
+	st95hf_send_st95enable_negativepulse(st95context);
+
+	/* wait for 10 milisecond : HFO setup time */
+	usleep_range(10000, 20000);
+
+	return result;
+}
+
+static int st95hf_por_sequence(struct st95hf_context *st95context)
+{
+	int nth_attempt = 1;
+	int result;
+
+	st95hf_send_st95enable_negativepulse(st95context);
+
+	usleep_range(5000, 6000);
+	do {
+		/* send an ECHO command and checks ST95HF response */
+		result = st95hf_echo_command(st95context);
+
+		dev_dbg(&st95context->spicontext.spidev->dev,
+			"response from echo function = 0x%x, attempt = %d\n",
+			result, nth_attempt);
+
+		if (!result)
+			return 0;
+
+		/* send an pulse on IRQ in case of the chip is on sleep state */
+		if (nth_attempt == 2)
+			st95hf_send_st95enable_negativepulse(st95context);
+		else
+			st95hf_send_spi_reset_sequence(st95context);
+
+		/* delay of 50 milisecond */
+		usleep_range(50000, 51000);
+	} while (nth_attempt++ < 3);
+
+	return -ETIMEDOUT;
+}
+
+static int iso14443_config_fdt(struct st95hf_context *st95context, int wtxm)
+{
+	int result = 0;
+	struct device *dev = &st95context->spicontext.spidev->dev;
+	struct nfc_digital_dev *nfcddev = st95context->ddev;
+	unsigned char pp_typeb;
+	struct param_list new_params[2];
+
+	pp_typeb = cmd_array[CMD_ISO14443B_PROTOCOL_SELECT].cmd_params[2];
+
+	if (nfcddev->curr_protocol == NFC_PROTO_ISO14443 &&
+	    st95context->fwi < 4)
+		st95context->fwi = 4;
+
+	new_params[0].param_offset = 2;
+	if (nfcddev->curr_protocol == NFC_PROTO_ISO14443)
+		new_params[0].new_param_val = st95context->fwi;
+	else if (nfcddev->curr_protocol == NFC_PROTO_ISO14443_B)
+		new_params[0].new_param_val = pp_typeb;
+
+	new_params[1].param_offset = 3;
+	new_params[1].new_param_val = wtxm;
+
+	switch (nfcddev->curr_protocol) {
+	case NFC_PROTO_ISO14443:
+		result = st95hf_send_recv_cmd(st95context,
+					      CMD_ISO14443A_PROTOCOL_SELECT,
+					      2,
+					      new_params,
+					      true);
+		if (result) {
+			dev_err(dev, "WTX type a sel proto, err = 0x%x\n",
+				result);
+			return result;
+		}
+
+		/* secondary config. for 14443Type 4A after protocol select */
+		result = secondary_configuration_type4a(st95context);
+		if (result) {
+			dev_err(dev, "WTX type a second. config, err = 0x%x\n",
+				result);
+			return result;
+		}
+		break;
+	case NFC_PROTO_ISO14443_B:
+		result = st95hf_send_recv_cmd(st95context,
+					      CMD_ISO14443B_PROTOCOL_SELECT,
+					      2,
+					      new_params,
+					      true);
+		if (result) {
+			dev_err(dev, "WTX type b sel proto, err = 0x%x\n",
+				result);
+			return result;
+		}
+
+		/* secondary config. for 14443Type 4B after protocol select */
+		result = secondary_configuration_type4b(st95context);
+		if (result) {
+			dev_err(dev, "WTX type b second. config, err = 0x%x\n",
+				result);
+			return result;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int st95hf_handle_wtx(struct st95hf_context *stcontext,
+			     bool new_wtx,
+			     int wtx_val)
+{
+	int result = 0;
+	unsigned char val_mm = 0;
+	struct param_list new_params[1];
+	struct nfc_digital_dev *nfcddev = stcontext->ddev;
+	struct device *dev = &stcontext->nfcdev->dev;
+
+	if (new_wtx) {
+		result = iso14443_config_fdt(stcontext, wtx_val & 0x3f);
+		if (result) {
+			dev_err(dev, "Config. setting error on WTX req, err = 0x%x\n",
+				result);
+			return result;
+		}
+
+		/* Send response of wtx with ASYNC as no response expected */
+		new_params[0].param_offset = 1;
+		new_params[0].new_param_val = wtx_val;
+
+		result = st95hf_send_recv_cmd(stcontext,
+					      CMD_WTX_RESPONSE,
+					      1,
+					      new_params,
+					      false);
+		if (result)
+			dev_err(dev, "WTX response send, err = 0x%x\n", result);
+		return result;
+	}
+
+	/* if no new wtx, cofigure with default values */
+	if (nfcddev->curr_protocol == NFC_PROTO_ISO14443)
+		val_mm = cmd_array[CMD_ISO14443A_PROTOCOL_SELECT].cmd_params[3];
+	else if (nfcddev->curr_protocol == NFC_PROTO_ISO14443_B)
+		val_mm = cmd_array[CMD_ISO14443B_PROTOCOL_SELECT].cmd_params[3];
+
+	result = iso14443_config_fdt(stcontext, val_mm);
+	if (result)
+		dev_err(dev, "Default config. setting error after WTX processing, err = 0x%x\n",
+			result);
+
+	return result;
+}
+
+static int st95hf_error_handling(struct st95hf_context *stcontext,
+				 struct sk_buff *skb_resp,
+				 int res_len)
+{
+	int result = 0;
+	unsigned char error_byte;
+	struct device *dev = &stcontext->nfcdev->dev;
+
+	/* First check ST95HF specific error */
+	if (skb_resp->data[0] & ST95HF_ERR_MASK) {
+		if (skb_resp->data[0] == ST95HF_TIMEOUT_ERROR)
+			result = -ETIMEDOUT;
+		else
+			result = -EIO;
+	return  result;
+	}
+
+	/* Check for CRC err only if CRC is present in the tag response */
+	switch (stcontext->current_rf_tech) {
+	case NFC_DIGITAL_RF_TECH_106A:
+		if (stcontext->sendrcv_trflag == TRFLAG_NFCA_STD_FRAME_CRC) {
+			error_byte = skb_resp->data[res_len - 3];
+			if (error_byte & ST95HF_NFCA_CRC_ERR_MASK) {
+				/* CRC error occurred */
+				dev_err(dev, "CRC error, byte received = 0x%x\n",
+					error_byte);
+				result = -EIO;
+			}
+		}
+		break;
+	case NFC_DIGITAL_RF_TECH_106B:
+	case NFC_DIGITAL_RF_TECH_ISO15693:
+		error_byte = skb_resp->data[res_len - 1];
+		if (error_byte & ST95HF_NFCB_CRC_ERR_MASK) {
+			/* CRC error occurred */
+			dev_err(dev, "CRC error, byte received = 0x%x\n",
+				error_byte);
+			result = -EIO;
+		}
+		break;
+	}
+
+	return result;
+}
+
+static int st95hf_response_handler(struct st95hf_context *stcontext,
+				   struct sk_buff *skb_resp,
+				   int res_len)
+{
+	int result = 0;
+	int skb_len;
+	unsigned char val_mm;
+	struct nfc_digital_dev *nfcddev = stcontext->ddev;
+	struct device *dev = &stcontext->nfcdev->dev;
+	struct st95_digital_cmd_complete_arg *cb_arg;
+
+	cb_arg = &stcontext->complete_cb_arg;
+
+	/* Process the response */
+	skb_put(skb_resp, res_len);
+
+	/* Remove st95 header */
+	skb_pull(skb_resp, 2);
+
+	skb_len = skb_resp->len;
+
+	/* check if it is case of RATS request reply & FWI is present */
+	if (nfcddev->curr_protocol == NFC_PROTO_ISO14443 && cb_arg->rats &&
+	    (skb_resp->data[1] & RATS_TB1_PRESENT_MASK)) {
+		if (skb_resp->data[1] & RATS_TA1_PRESENT_MASK)
+			stcontext->fwi =
+				(skb_resp->data[3] & TB1_FWI_MASK) >> 4;
+		else
+			stcontext->fwi =
+				(skb_resp->data[2] & TB1_FWI_MASK) >> 4;
+
+		val_mm = cmd_array[CMD_ISO14443A_PROTOCOL_SELECT].cmd_params[3];
+
+		result = iso14443_config_fdt(stcontext, val_mm);
+		if (result) {
+			dev_err(dev, "error in config_fdt to handle fwi of ATS, error=%d\n",
+				result);
+			return result;
+		}
+	}
+	cb_arg->rats = false;
+
+	/* Remove CRC bytes only if received frames data has an eod (CRC) */
+	switch (stcontext->current_rf_tech) {
+	case NFC_DIGITAL_RF_TECH_106A:
+		if (stcontext->sendrcv_trflag == TRFLAG_NFCA_STD_FRAME_CRC)
+			skb_trim(skb_resp, (skb_len - 5));
+		else
+			skb_trim(skb_resp, (skb_len - 3));
+		break;
+	case NFC_DIGITAL_RF_TECH_106B:
+	case NFC_DIGITAL_RF_TECH_ISO15693:
+		skb_trim(skb_resp, (skb_len - 3));
+		break;
+	}
+
+	return result;
+}
+
+static irqreturn_t irq_handler(int irq, void  *st95hfcontext)
+{
+	struct st95hf_context *stcontext  =
+		(struct st95hf_context *)st95hfcontext;
+
+	if (stcontext->spicontext.req_issync) {
+		complete(&stcontext->spicontext.done);
+		stcontext->spicontext.req_issync = false;
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t irq_thread_handler(int irq, void  *st95hfcontext)
+{
+	int result = 0;
+	int res_len;
+	static bool wtx;
+	struct device *dev;
+	struct device *spidevice;
+	struct nfc_digital_dev *nfcddev;
+	struct sk_buff *skb_resp;
+	struct st95hf_context *stcontext  =
+		(struct st95hf_context *)st95hfcontext;
+	struct st95_digital_cmd_complete_arg *cb_arg;
+
+	spidevice = &stcontext->spicontext.spidev->dev;
+
+	/*
+	 * check semaphore, if not down() already, then we don't
+	 * know in which context the ISR is called and surely it
+	 * will be a bug. Note that down() of the semaphore is done
+	 * in the corresponding st95hf_in_send_cmd() and then
+	 * only this ISR should be called. ISR will up() the
+	 * semaphore before leaving. Hence when the ISR is called
+	 * the correct behaviour is down_trylock() should always
+	 * return 1 (indicating semaphore cant be taken and hence no
+	 * change in semaphore count).
+	 * If not, then we up() the semaphore and crash on
+	 * a BUG() !
+	 */
+	if (!down_trylock(&stcontext->exchange_lock)) {
+		up(&stcontext->exchange_lock);
+		WARN(1, "unknown context in ST95HF ISR");
+		return IRQ_NONE;
+	}
+
+	cb_arg = &stcontext->complete_cb_arg;
+	skb_resp = cb_arg->skb_resp;
+
+	mutex_lock(&stcontext->rm_lock);
+	res_len = st95hf_spi_recv_response(&stcontext->spicontext,
+					   skb_resp->data);
+	if (res_len < 0) {
+		dev_err(spidevice, "TISR spi response err = 0x%x\n", res_len);
+		result = res_len;
+		goto end;
+	}
+
+	/* if stcontext->nfcdev_free is true, it means remove already ran */
+	if (stcontext->nfcdev_free) {
+		result = -ENODEV;
+		goto end;
+	}
+
+	dev = &stcontext->nfcdev->dev;
+	nfcddev = stcontext->ddev;
+	if (skb_resp->data[2] == WTX_REQ_FROM_TAG) {
+		/* Request for new FWT from tag */
+		result = st95hf_handle_wtx(stcontext, true, skb_resp->data[3]);
+		if (result)
+			goto end;
+
+		wtx = true;
+		mutex_unlock(&stcontext->rm_lock);
+		return IRQ_HANDLED;
+	}
+
+	result = st95hf_error_handling(stcontext, skb_resp, res_len);
+	if (result)
+		goto end;
+
+	result = st95hf_response_handler(stcontext, skb_resp, res_len);
+	if (result)
+		goto end;
+
+	/*
+	 * If select protocol is done on wtx req. do select protocol
+	 * again with default values
+	 */
+	if (wtx) {
+		wtx = false;
+		result = st95hf_handle_wtx(stcontext, false, 0);
+		if (result)
+			goto end;
+	}
+
+	/* call digital layer callback */
+	cb_arg->complete_cb(stcontext->ddev, cb_arg->cb_usrarg, skb_resp);
+
+	/* up the semaphore before returning */
+	up(&stcontext->exchange_lock);
+	mutex_unlock(&stcontext->rm_lock);
+
+	return IRQ_HANDLED;
+
+end:
+	kfree_skb(skb_resp);
+	wtx = false;
+	cb_arg->rats = false;
+	skb_resp = ERR_PTR(result);
+	/* call of callback with error */
+	cb_arg->complete_cb(stcontext->ddev, cb_arg->cb_usrarg, skb_resp);
+	/* up the semaphore before returning */
+	up(&stcontext->exchange_lock);
+	mutex_unlock(&stcontext->rm_lock);
+	return IRQ_HANDLED;
+}
+
+/* NFC ops functions definition */
+static int st95hf_in_configure_hw(struct nfc_digital_dev *ddev,
+				  int type,
+				  int param)
+{
+	struct st95hf_context *stcontext = nfc_digital_get_drvdata(ddev);
+
+	if (type == NFC_DIGITAL_CONFIG_RF_TECH)
+		return st95hf_select_protocol(stcontext, param);
+
+	if (type == NFC_DIGITAL_CONFIG_FRAMING) {
+		switch (param) {
+		case NFC_DIGITAL_FRAMING_NFCA_SHORT:
+			stcontext->sendrcv_trflag = TRFLAG_NFCA_SHORT_FRAME;
+			break;
+		case NFC_DIGITAL_FRAMING_NFCA_STANDARD:
+			stcontext->sendrcv_trflag = TRFLAG_NFCA_STD_FRAME;
+			break;
+		case NFC_DIGITAL_FRAMING_NFCA_T4T:
+		case NFC_DIGITAL_FRAMING_NFCA_NFC_DEP:
+		case NFC_DIGITAL_FRAMING_NFCA_STANDARD_WITH_CRC_A:
+			stcontext->sendrcv_trflag = TRFLAG_NFCA_STD_FRAME_CRC;
+			break;
+		case NFC_DIGITAL_FRAMING_NFCB:
+		case NFC_DIGITAL_FRAMING_ISO15693_INVENTORY:
+		case NFC_DIGITAL_FRAMING_ISO15693_T5T:
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static int rf_off(struct st95hf_context *stcontext)
+{
+	int rc;
+	struct device *dev;
+
+	dev = &stcontext->nfcdev->dev;
+
+	rc = st95hf_send_recv_cmd(stcontext, CMD_FIELD_OFF, 0, NULL, true);
+	if (rc)
+		dev_err(dev, "protocol sel send field off, err = 0x%x\n", rc);
+
+	return rc;
+}
+
+static int st95hf_in_send_cmd(struct nfc_digital_dev *ddev,
+			      struct sk_buff *skb,
+			      u16 timeout,
+			      nfc_digital_cmd_complete_t cb,
+			      void *arg)
+{
+	struct st95hf_context *stcontext = nfc_digital_get_drvdata(ddev);
+	int rc;
+	struct sk_buff *skb_resp;
+	int len_data_to_tag = 0;
+
+	skb_resp = nfc_alloc_recv_skb(MAX_RESPONSE_BUFFER_SIZE, GFP_KERNEL);
+	if (!skb_resp) {
+		rc = -ENOMEM;
+		goto error;
+	}
+
+	switch (stcontext->current_rf_tech) {
+	case NFC_DIGITAL_RF_TECH_106A:
+		len_data_to_tag = skb->len + 1;
+		*skb_put(skb, 1) = stcontext->sendrcv_trflag;
+		break;
+	case NFC_DIGITAL_RF_TECH_106B:
+	case NFC_DIGITAL_RF_TECH_ISO15693:
+		len_data_to_tag = skb->len;
+		break;
+	default:
+		rc = -EINVAL;
+		goto free_skb_resp;
+	}
+
+	skb_push(skb, 3);
+	skb->data[0] = ST95HF_COMMAND_SEND;
+	skb->data[1] = SEND_RECEIVE_CMD;
+	skb->data[2] = len_data_to_tag;
+
+	stcontext->complete_cb_arg.skb_resp = skb_resp;
+	stcontext->complete_cb_arg.cb_usrarg = arg;
+	stcontext->complete_cb_arg.complete_cb = cb;
+
+	if ((skb->data[3] == ISO14443A_RATS_REQ) &&
+	    ddev->curr_protocol == NFC_PROTO_ISO14443)
+		stcontext->complete_cb_arg.rats = true;
+
+	/*
+	 * down the semaphore to indicate to remove func that an
+	 * ISR is pending, note that it will not block here in any case.
+	 * If found blocked, it is a BUG!
+	 */
+	rc = down_killable(&stcontext->exchange_lock);
+	if (rc) {
+		WARN(1, "Semaphore is not found up in st95hf_in_send_cmd\n");
+		return rc;
+	}
+
+	rc = st95hf_spi_send(&stcontext->spicontext, skb->data,
+			     skb->len,
+			     ASYNC);
+	if (rc) {
+		dev_err(&stcontext->nfcdev->dev,
+			"Error %d trying to perform data_exchange", rc);
+		/* up the semaphore since ISR will never come in this case */
+		up(&stcontext->exchange_lock);
+		goto free_skb_resp;
+	}
+
+	kfree_skb(skb);
+
+	return rc;
+
+free_skb_resp:
+	kfree_skb(skb_resp);
+error:
+	return rc;
+}
+
+/* p2p will be supported in a later release ! */
+static int st95hf_tg_configure_hw(struct nfc_digital_dev *ddev,
+				  int type,
+				  int param)
+{
+	return 0;
+}
+
+static int st95hf_tg_send_cmd(struct nfc_digital_dev *ddev,
+			      struct sk_buff *skb,
+			      u16 timeout,
+			      nfc_digital_cmd_complete_t cb,
+			      void *arg)
+{
+	return 0;
+}
+
+static int st95hf_tg_listen(struct nfc_digital_dev *ddev,
+			    u16 timeout,
+			    nfc_digital_cmd_complete_t cb,
+			    void *arg)
+{
+	return 0;
+}
+
+static int st95hf_tg_get_rf_tech(struct nfc_digital_dev *ddev, u8 *rf_tech)
+{
+	return 0;
+}
+
+static int st95hf_switch_rf(struct nfc_digital_dev *ddev, bool on)
+{
+	u8 rf_tech;
+	struct st95hf_context *stcontext = nfc_digital_get_drvdata(ddev);
+
+	rf_tech = ddev->curr_rf_tech;
+
+	if (on)
+		/* switch on RF field */
+		return st95hf_select_protocol(stcontext, rf_tech);
+
+	/* switch OFF RF field */
+	return rf_off(stcontext);
+}
+
+/* TODO st95hf_abort_cmd */
+static void st95hf_abort_cmd(struct nfc_digital_dev *ddev)
+{
+}
+
+static struct nfc_digital_ops st95hf_nfc_digital_ops = {
+	.in_configure_hw = st95hf_in_configure_hw,
+	.in_send_cmd = st95hf_in_send_cmd,
+
+	.tg_listen = st95hf_tg_listen,
+	.tg_configure_hw = st95hf_tg_configure_hw,
+	.tg_send_cmd = st95hf_tg_send_cmd,
+	.tg_get_rf_tech = st95hf_tg_get_rf_tech,
+
+	.switch_rf = st95hf_switch_rf,
+	.abort_cmd = st95hf_abort_cmd,
+};
+
+static const struct spi_device_id st95hf_id[] = {
+	{ "st95hf", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, st95hf_id);
+
+static int st95hf_probe(struct spi_device *nfc_spi_dev)
+{
+	int ret;
+
+	struct st95hf_context *st95context;
+	struct st95hf_spi_context *spicontext;
+
+	nfc_info(&nfc_spi_dev->dev, "ST95HF driver probe called.\n");
+
+	st95context = devm_kzalloc(&nfc_spi_dev->dev,
+				   sizeof(struct st95hf_context),
+				   GFP_KERNEL);
+	if (!st95context)
+		return -ENOMEM;
+
+	spicontext = &st95context->spicontext;
+
+	spicontext->spidev = nfc_spi_dev;
+
+	st95context->fwi =
+		cmd_array[CMD_ISO14443A_PROTOCOL_SELECT].cmd_params[2];
+
+	if (device_property_present(&nfc_spi_dev->dev, "st95hfvin")) {
+		st95context->st95hf_supply =
+			devm_regulator_get(&nfc_spi_dev->dev,
+					   "st95hfvin");
+		if (IS_ERR(st95context->st95hf_supply)) {
+			dev_err(&nfc_spi_dev->dev, "failed to acquire regulator\n");
+			return PTR_ERR(st95context->st95hf_supply);
+		}
+
+		ret = regulator_enable(st95context->st95hf_supply);
+		if (ret) {
+			dev_err(&nfc_spi_dev->dev, "failed to enable regulator\n");
+			return ret;
+		}
+	}
+
+	init_completion(&spicontext->done);
+	mutex_init(&spicontext->spi_lock);
+
+	/*
+	 * Store spicontext in spi device object for using it in
+	 * remove function
+	 */
+	dev_set_drvdata(&nfc_spi_dev->dev, spicontext);
+
+	st95context->enable_gpio =
+		of_get_named_gpio(nfc_spi_dev->dev.of_node,
+				  "enable-gpio",
+				  0);
+	if (!gpio_is_valid(st95context->enable_gpio)) {
+		dev_err(&nfc_spi_dev->dev, "No valid enable gpio\n");
+		ret = st95context->enable_gpio;
+		goto err_disable_regulator;
+	}
+
+	ret = devm_gpio_request_one(&nfc_spi_dev->dev, st95context->enable_gpio,
+				    GPIOF_DIR_OUT | GPIOF_INIT_HIGH,
+				    "enable_gpio");
+	if (ret)
+		goto err_disable_regulator;
+
+	if (nfc_spi_dev->irq > 0) {
+		if (devm_request_threaded_irq(&nfc_spi_dev->dev,
+					      nfc_spi_dev->irq,
+					      irq_handler,
+					      irq_thread_handler,
+					      IRQF_TRIGGER_FALLING,
+					      "st95hf",
+					      (void *)st95context) < 0) {
+			dev_err(&nfc_spi_dev->dev, "err: irq request for st95hf is failed\n");
+			ret =  -EINVAL;
+			goto err_disable_regulator;
+		}
+	} else {
+		dev_err(&nfc_spi_dev->dev, "not a valid IRQ associated with ST95HF\n");
+		ret = -EINVAL;
+		goto err_disable_regulator;
+	}
+
+	/*
+	 * First reset SPI to handle warm reset of the system.
+	 * It will put the ST95HF device in Power ON state
+	 * which make the state of device identical to state
+	 * at the time of cold reset of the system.
+	 */
+	ret = st95hf_send_spi_reset_sequence(st95context);
+	if (ret) {
+		dev_err(&nfc_spi_dev->dev, "err: spi_reset_sequence failed\n");
+		goto err_disable_regulator;
+	}
+
+	/* call PowerOnReset sequence of ST95hf to activate it */
+	ret = st95hf_por_sequence(st95context);
+	if (ret) {
+		dev_err(&nfc_spi_dev->dev, "err: por seq failed for st95hf\n");
+		goto err_disable_regulator;
+	}
+
+	/* create NFC dev object and register with NFC Subsystem */
+	st95context->ddev = nfc_digital_allocate_device(&st95hf_nfc_digital_ops,
+							ST95HF_SUPPORTED_PROT,
+							ST95HF_CAPABILITIES,
+							ST95HF_HEADROOM_LEN,
+							ST95HF_TAILROOM_LEN);
+	if (!st95context->ddev) {
+		ret = -ENOMEM;
+		goto err_disable_regulator;
+	}
+
+	st95context->nfcdev = st95context->ddev->nfc_dev;
+	nfc_digital_set_parent_dev(st95context->ddev, &nfc_spi_dev->dev);
+
+	ret =  nfc_digital_register_device(st95context->ddev);
+	if (ret) {
+		dev_err(&st95context->nfcdev->dev, "st95hf registration failed\n");
+		goto err_free_digital_device;
+	}
+
+	/* store st95context in nfc device object */
+	nfc_digital_set_drvdata(st95context->ddev, st95context);
+
+	sema_init(&st95context->exchange_lock, 1);
+	mutex_init(&st95context->rm_lock);
+
+	return ret;
+
+err_free_digital_device:
+	nfc_digital_free_device(st95context->ddev);
+err_disable_regulator:
+	if (st95context->st95hf_supply)
+		regulator_disable(st95context->st95hf_supply);
+
+	return ret;
+}
+
+static int st95hf_remove(struct spi_device *nfc_spi_dev)
+{
+	int result = 0;
+	unsigned char reset_cmd = ST95HF_COMMAND_RESET;
+	struct st95hf_spi_context *spictx = dev_get_drvdata(&nfc_spi_dev->dev);
+
+	struct st95hf_context *stcontext = container_of(spictx,
+							struct st95hf_context,
+							spicontext);
+
+	mutex_lock(&stcontext->rm_lock);
+
+	nfc_digital_unregister_device(stcontext->ddev);
+	nfc_digital_free_device(stcontext->ddev);
+	stcontext->nfcdev_free = true;
+
+	mutex_unlock(&stcontext->rm_lock);
+
+	/* if last in_send_cmd's ISR is pending, wait for it to finish */
+	result = down_killable(&stcontext->exchange_lock);
+	if (result == -EINTR)
+		dev_err(&spictx->spidev->dev, "sleep for semaphore interrupted by signal\n");
+
+	/* next reset the ST95HF controller */
+	result = st95hf_spi_send(&stcontext->spicontext,
+				 &reset_cmd,
+				 ST95HF_RESET_CMD_LEN,
+				 ASYNC);
+	if (result) {
+		dev_err(&spictx->spidev->dev,
+			"ST95HF reset failed in remove() err = %d\n", result);
+		return result;
+	}
+
+	/* wait for 3 ms to complete the controller reset process */
+	usleep_range(3000, 4000);
+
+	/* disable regulator */
+	if (stcontext->st95hf_supply)
+		regulator_disable(stcontext->st95hf_supply);
+
+	return result;
+}
+
+/* Register as SPI protocol driver */
+static struct spi_driver st95hf_driver = {
+	.driver = {
+		.name = "st95hf",
+		.owner = THIS_MODULE,
+	},
+	.id_table = st95hf_id,
+	.probe = st95hf_probe,
+	.remove = st95hf_remove,
+};
+
+module_spi_driver(st95hf_driver);
+
+MODULE_AUTHOR("Shikha Singh <[e-mail]>");
+MODULE_DESCRIPTION("ST NFC Transceiver ST95HF driver");
+MODULE_LICENSE("GPL v2");

drivers/nfc/st95hf/spi.c

···
+/*
+ * ----------------------------------------------------------------------------
+ * drivers/nfc/st95hf/spi.c function definitions for SPI communication
+ * ----------------------------------------------------------------------------
+ * Copyright (C) 2015 STMicroelectronics Pvt. Ltd. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "spi.h"
+
+/* Function to send user provided buffer to ST95HF through SPI */
+int st95hf_spi_send(struct st95hf_spi_context *spicontext,
+		    unsigned char *buffertx,
+		    int datalen,
+		    enum req_type reqtype)
+{
+	struct spi_message m;
+	int result = 0;
+	struct spi_device *spidev = spicontext->spidev;
+	struct spi_transfer tx_transfer = {
+		.tx_buf = buffertx,
+		.len = datalen,
+	};
+
+	mutex_lock(&spicontext->spi_lock);
+
+	if (reqtype == SYNC) {
+		spicontext->req_issync = true;
+		reinit_completion(&spicontext->done);
+	} else {
+		spicontext->req_issync = false;
+	}
+
+	spi_message_init(&m);
+	spi_message_add_tail(&tx_transfer, &m);
+
+	result = spi_sync(spidev, &m);
+	if (result) {
+		dev_err(&spidev->dev, "error: sending cmd to st95hf using SPI = %d\n",
+			result);
+		mutex_unlock(&spicontext->spi_lock);
+		return result;
+	}
+
+	/* return for asynchronous or no-wait case */
+	if (reqtype == ASYNC) {
+		mutex_unlock(&spicontext->spi_lock);
+		return 0;
+	}
+
+	result = wait_for_completion_timeout(&spicontext->done,
+					     msecs_to_jiffies(1000));
+	/* check for timeout or success */
+	if (!result) {
+		dev_err(&spidev->dev, "error: response not ready timeout\n");
+		result = -ETIMEDOUT;
+	} else {
+		result = 0;
+	}
+
+	mutex_unlock(&spicontext->spi_lock);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(st95hf_spi_send);
+
+/* Function to Receive command Response */
+int st95hf_spi_recv_response(struct st95hf_spi_context *spicontext,
+			     unsigned char *receivebuff)
+{
+	int len = 0;
+	struct spi_transfer tx_takedata;
+	struct spi_message m;
+	struct spi_device *spidev = spicontext->spidev;
+	unsigned char readdata_cmd = ST95HF_COMMAND_RECEIVE;
+	struct spi_transfer t[2] = {
+		{.tx_buf = &readdata_cmd, .len = 1,},
+		{.rx_buf = receivebuff, .len = 2, .cs_change = 1,},
+	};
+
+	int ret = 0;
+
+	memset(&tx_takedata, 0x0, sizeof(struct spi_transfer));
+
+	mutex_lock(&spicontext->spi_lock);
+
+	/* First spi transfer to know the length of valid data */
+	spi_message_init(&m);
+	spi_message_add_tail(&t[0], &m);
+	spi_message_add_tail(&t[1], &m);
+
+	ret = spi_sync(spidev, &m);
+	if (ret) {
+		dev_err(&spidev->dev, "spi_recv_resp, data length error = %d\n",
+			ret);
+		mutex_unlock(&spicontext->spi_lock);
+		return ret;
+	}
+
+	/* As 2 bytes are already read */
+	len = 2;
+
+	/* Support of long frame */
+	if (receivebuff[0] & 0x60)
+		len += (((receivebuff[0] & 0x60) >> 5) << 8) | receivebuff[1];
+	else
+		len += receivebuff[1];
+
+	/* Now make a transfer to read only relevant bytes */
+	tx_takedata.rx_buf = &receivebuff[2];
+	tx_takedata.len = len - 2;
+
+	spi_message_init(&m);
+	spi_message_add_tail(&tx_takedata, &m);
+
+	ret = spi_sync(spidev, &m);
+
+	mutex_unlock(&spicontext->spi_lock);
+	if (ret) {
+		dev_err(&spidev->dev, "spi_recv_resp, data read error = %d\n",
+			ret);
+		return ret;
+	}
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(st95hf_spi_recv_response);
+
+int st95hf_spi_recv_echo_res(struct st95hf_spi_context *spicontext,
+			     unsigned char *receivebuff)
+{
+	unsigned char readdata_cmd = ST95HF_COMMAND_RECEIVE;
+	struct spi_transfer t[2] = {
+		{.tx_buf = &readdata_cmd, .len = 1,},
+		{.rx_buf = receivebuff, .len = 1,},
+	};
+	struct spi_message m;
+	struct spi_device *spidev = spicontext->spidev;
+	int ret = 0;
+
+	mutex_lock(&spicontext->spi_lock);
+
+	spi_message_init(&m);
+	spi_message_add_tail(&t[0], &m);
+	spi_message_add_tail(&t[1], &m);
+	ret = spi_sync(spidev, &m);
+
+	mutex_unlock(&spicontext->spi_lock);
+
+	if (ret)
+		dev_err(&spidev->dev, "recv_echo_res, data read error = %d\n",
+			ret);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(st95hf_spi_recv_echo_res);

drivers/nfc/st95hf/spi.h

···
+/*
+ * ---------------------------------------------------------------------------
+ * drivers/nfc/st95hf/spi.h functions declarations for SPI communication
+ * ---------------------------------------------------------------------------
+ * Copyright (C) 2015 STMicroelectronics – All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __LINUX_ST95HF_SPI_H
+#define __LINUX_ST95HF_SPI_H
+
+#include <linux/spi/spi.h>
+
+/* Basic ST95HF SPI CMDs */
+#define ST95HF_COMMAND_SEND	0x0
+#define ST95HF_COMMAND_RESET	0x1
+#define ST95HF_COMMAND_RECEIVE	0x2
+
+#define ST95HF_RESET_CMD_LEN	0x1
+
+/*
+ * structure to contain st95hf spi communication specific information.
+ * @req_issync: true for synchronous calls.
+ * @spidev: st95hf spi device object.
+ * @done: completion structure to wait for st95hf response
+ *	for synchronous calls.
+ * @spi_lock: mutex to allow only one spi transfer at a time.
+ */
+struct st95hf_spi_context {
+	bool req_issync;
+	struct spi_device *spidev;
+	struct completion done;
+	struct mutex spi_lock;
+};
+
+/* flag to differentiate synchronous & asynchronous spi request */
+enum req_type {
+	SYNC,
+	ASYNC,
+};
+
+int st95hf_spi_send(struct st95hf_spi_context *spicontext,
+		    unsigned char *buffertx,
+		    int datalen,
+		    enum req_type reqtype);
+
+int st95hf_spi_recv_response(struct st95hf_spi_context *spicontext,
+			     unsigned char *receivebuff);
+
+int st95hf_spi_recv_echo_res(struct st95hf_spi_context *spicontext,
+			     unsigned char *receivebuff);
+
+#endif